The laying of railway track, either in the initial construction of a railway line or when replacing existing rails, is necessarily a difficult, time consuming and labor intensive job. Standard industry practice involves constructing individual rail sections and then welding them together end to end to form lengthy ribbon rails that may be as long as 1800 feet or more.
The ribbon rails have traditionally been transported to their installation site by transporting them along the railway and loading them onto special rail cars equipped with bunks that receive the rails on several different tiers. The rails are unloaded from the special car side-by-side in pairs using equipment that conventionally includes a complicated winch, thread box and pulley system. The rails are unloaded from the special car using this complicated equipment in a time consuming process that involves repeated starts and stops of the locomotive that pulls the special rail unloading car along the track, and manual handling of the rails and equipment.
This conventional practice is problematic in several respects. It requires significant manual labor to handle the equipment and connect it with the rails, and workers are subjected to the risk of serious injury because they must physically be present at the site of the operations that are carried out. The time required to unload the rails in this manner adds significantly to both the labor costs and to the overall maintenance costs of the railway.
Although equipment has been proposed to attempt to automate the process more fully and reduce the need for extensive manual labor and the risk of personal injury, such equipment has not been wholly satisfactory. For example, U.S. Pat. Nos. 5,227,435 and 6,981,452 to Theurer, et al. disclose complicated rail unloading machines that include complexities such as cable and pulley systems, specially constructed crawlers, and conveyor systems of various types. Aside from the cost and maintenance problems resulting from the need for such complicated machinery, the Theurer equipment operates only on railway track. Consequently, when the rails need to be transported over lengthy distances, they are restricted to rail transportation and cannot be transported over-the-road along highways or other roadways that may be a more efficient mode of transportation.
More recently, a rail unloading machine has been developed for travel interchangeably along a railway or a roadway, as disclosed in U.S. Pat. No. 6,981,452 to Herzog, et al. Although this Herzog machine is a substantial improvement because of the versatility it offers with respect to modes of transportation, it is not self-propelled but instead requires one type of vehicle to transport it on a roadway and another vehicle such as a locomotive to transport it along a railway. Accordingly, there is a need to couple and uncouple the rail unloading equipment from the different towing vehicles required for the different modes of travel, and this adds to the time, cost and complexity of the entire operation.
Additionally, it is desirable for a pair of rails to be unloaded simultaneously on opposite sides of the rail bed outwardly of the rails and rail ties that are already in place. To accomplish this, the thread boxes must be spaced apart far enough to enable the rails to be unloaded outwardly of the rails and the ends of the ties that are installed on the rail bed, and this can result in equipment that is too wide to travel safely on many roadways.